The present invention relates to locking devices for tools, such as sawblades, and in particular to a locking device for tools of the split type, which comprise two or more segments held together during use.
In commercial woodworking shops of the type where high production articles are being made, such as furniture making factories, circular saws are running nearly constantly, and the blades tend to wear rapidly, thereby requiring frequent replacement. Since the replacement of a blade necessitates shutting the machine down, the longer this procedure takes, the more production time which is lost. To minimize the time which is required to make a blade change, the blades have, in the past, been of the split variety comprising two semi-circular halves. To change a blade of this type, it is not necessary to remove the entire blade axially from the arbor, but merely to loosen the locking ring so that the two halves can be separated radially from the arbor.
Because sawblades utilized in high production woodworking installations are quite large, for example, fourteen inches to sixteen inches in diameter, and rotate at high speeds, a considerable amount of centrifugal force is generated. Obviously, this force would tend to separate the two halves of the blade thereby posing a very serious safety problem. One type of prior art collar comprises a split collar, which engages the blade halves by means of dowels or pins, and which is bolted together by means of bolts extending transversely to the axis of the blade. Because of the trememdous centrifugal forces generated by the rotating mass of the blade halves, however, these bolts are stressed to the point that they begin to stretch. When this occurs, the bolts could break thereby permitting the blade halves to fly off the arbor. Even if the bolts would not break, the outward movement of the collars may cause unusual stresses to be developed in the pins or dowels connecting them to the blade halves so that failure of the dowels or pins may occur.